<html>
<body>
<div style="background: red; height: 4000px;">hi</div>
<div id="b" style="background: blue; height: 10000px;"></div>
<div id="a" style="background: yellow; height: 100px;"></div>
<div style="background: green; height: 4000px;"></div>
</body>
</html>
